The Rozière, a sophisticated hybrid balloon
Rozière-type balloons are named after Pilâtre de Rozier, who was the first to combine a hot-air balloon and a conventional gas balloon. A Rozière relies on an envelope of gas that is lighter than air (usually helium), and this envelope is dilated by means of a cone of hot air that is heated using a small burner. The advantage of a Rozière is that it requires very little energy input; lift is provided by the helium and hot air is used only to maintain optimum dilation of the envelope of helium so that the balloon remains at the required height. This means the balloon can fly much further than a conventional hot-air balloon, which can remain aloft for only a few hours. The Rozière used by Jean-Louis Etienne can remain in the air for about 20 days.

In theory, a balloon of this type can rise to an altitude of about 11,000 metres. The only problem for Jean-Louis Etienne would be the lack of pressurization. However, he will be carrying an additional supply of oxygen to allow him to fly for short periods in the upper atmosphere.

The nacelle, a cramped living space
The balloon’s nacelle, or pod, designed by Gérard Guérin, has an aluminium frame covered with a sandwich material made of fibreglass and 5-cm thick panels of polyurethane foam so as the provide the best possible thermal insulation.

The only other provision for comfort is a bench that doubles as a bed, placed opposite a console housing navigation and communication equipment. Jean-Louis Etienne will have a choice of three positions: lying down, sitting or standing up (but with no room to walk around…). A small propane heater will keep the temperature inside the nacelle at 15°C. A transparent Perspex dome in the top of the nacelle will allow the balloonist to verify the envelope and the burners from inside.